Heretofore, a copper-lead based bearing alloy material which has been used for an internal combustion engine has been widely applied to a high-speed, high-load engine. Its compositions are classified into a Cu--Pb alloy, a Cu--Sn--Pb alloy and a Cu--Bi--Pb alloy. Also, it has been known to provide an overlay of a Pb--Sn, Pb--Sn--Cu or Pb--Sn--In alloy on a copper-lead based alloy surface in order to make up for its conformability, seizure resistance, embedability, and corrosion resistance.
The lead contained in a copper-lead based bearing alloy is a metal which satisfies the requirements of conformability, seizure resistance, embedability and the like, but on the other hand it has the disadvantage that it makes the bearing poor in corrosion resistance. Specifically, due to a deterioration of lubricating oil, there is caused the danger of inducing the wear and seizure for the reason of the corrosion of Pb in the copper-lead based alloy. While an alloy is proposed in Japanese Unexamined Patent Publication No. 4-202726 so as to improve the corrosion resistance, the small amount of Pb added thereto does not satisfy the conformability and seizure resistance which are important for a bearing.